CDMS Computing
Astronomical and cosmological observations lead to the conclusion that
our galaxy is embedded in a halo of Cold Dark Matter (CDM). Several theories of
particle physics, such as Supersymmetry, predict the existence of Weakly
Interacting Massive Particles (WIMPs) with properties suitable for explaining
the CDM halo. The goal of the Cryogenic Dark Matter Search (CDMS) experiment is
to directly detect WIMPs in our halo by measuring nuclear recoils from
WIMP-nucleus interactions.
The CDMS strategy is to measure both the phonon energy and charge energy
of events in Germanium and Silicon crystals. A dilution refrigerator cools the
detectors to 50 mK to allow a precise measurement of the phonon energy down to
a 10 KeV threshold. The phonon channel measures the total energy of an event,
while the charge channel provides discrimination between nuclear and electron
recoils. The dense energy deposition from a slow-moving nuclear recoil produces
only 1/3 of the ionization of a relativistic electron recoil with the same
energy. Furthermore, the CDMS detectors measure the arrival time of phonons
from the recoil, allowing us to identify and reject backgrounds produced at the
surfaces of our detectors.
CDMS is currently taking data with 5 kg of target mass in the Soudan
mine in Northern Minnesota. The overburden of rock reduces the number of cosmic
ray muons, which would yield neutron backgrounds if they interacted near our
detectors. An active scintillator shield
vetoes events in coincidence with the remaining cosmic-ray flux. Further layers
of lead and polyethylene absorb ambient gamma and neutron radioactivity. CDMS
is the only operating direct-detection experiment with <1 event background,
and hence has the world’s best sensitivity for WIMP masses and interactions
that are most likely to constitute dark matter.
We arecurrently
in the early stages of review for construction of the next phase of our
experiment, SuperCDMS, which will use larger detectors for a total of 25 kg of
active mass, and will be located in a deeper site at Snolab in Canada. SuperCDMS
will have an order of magnitude better sensitivity to WIMPS than any current
experiment.
More Information: CDMS Experiment Home
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Last updated by cdweb on 04/29/2008
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